ImagePlacer is a very powerful publishing tool which allows you to stamp a graphical image onto specified pages within a PDF document. The graphic can be stamped as an overlay, or as a watermark. Overlays appear in the foreground of the appropriate page. Watermarks appear in the background of the appropriate page behind any existing text. Images stamped as an overlay can also be transparent. This means that the text beneath the graphic can still be seen/read.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.